title: Ugo1 and Mdm30 act sequentially during Fzo1-mediated mitochondrial outer membrane fusion.
abstract: Dynamin-related GTPase proteins (DRPs) are main players in membrane remodelling. Conserved DRPs called mitofusins (Mfn1/Mfn2/Fzo1) mediate the fusion of mitochondrial outer membranes (OM). OM fusion depends on self-assembly and GTPase activity of mitofusins as well as on two other proteins, Ugo1 and Mdm30. Here, we define distinct steps of the OM fusion cycle using in vitro and in vivo approaches. We demonstrate that yeast Fzo1 assembles into homo-dimers, depending on Ugo1 and on GTP binding to Fzo1. Fzo1 homo-dimers further associate upon formation of mitochondrial contacts, allowing membrane tethering. Subsequent GTP hydrolysis is required for Fzo1 ubiquitylation by the F-box protein Mdm30. Finally, Mdm30-dependent degradation of Fzo1 completes Fzo1 function in OM fusion. Our results thus unravel functions of Ugo1 and Mdm30 at distinct steps during OM fusion and suggest that protein clearance confers a non-cycling mechanism to mitofusins, which is distinct from other cellular membrane fusion events.
authors.affiliation: Institute for Genetics, University of Cologne, 50674 Cologne, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Anton
authors.forename: Julia M
authors.initials: JM
authors.lastname: Fres
authors.forename: Astrid
authors.initials: A
authors.lastname: Schauss
authors.forename: Benoît
authors.initials: B
authors.lastname: Pinson
authors.forename: Gerrit J K
authors.initials: GJ
authors.lastname: Praefcke
authors.forename: Thomas
authors.initials: T
authors.lastname: Langer
authors.forename: Mafalda
authors.initials: M
authors.lastname: Escobar-Henriques
mesh_terms: D000595:Amino Acid Sequence; D019281:Dimerization; D044783:F-Box Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000737:chemistry / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: D044783:F-Box Proteins; C481653:Mdm30 protein, S cerevisiae; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins; C423986:UGO1 protein, S cerevisiae; D006160:Guanosine Triphosphate; C401395:FZO1 protein, S cerevisiae; D020558:GTP Phosphohydrolases